The NCA’s deputy director Chris McKeogh said in November that trials had collapsed due to incompetence.
Photograph: PA

Britain’s national law enforcement agency has been heavily criticised by MPs after the collapse of major trials and struggles to cope with its huge caseload.

The National Crime Agency (NCA) is reviewing around 350 operations after court cases fell apart due to the way investigations were carried out.

It is being sued over issues with warrants that judges said exposed systemic ignorance over basic investigation procedures that was “difficult to believe”.

About 2,000 documents are being examined and some lower level issues have been found in the review after cases collapsed following Operations Heterodon and Enderby.

The Commons home affairs select committee was also told IT systems are struggling to cope with the huge number of cases the NCA is dealing with.

About 20,000 serious crime referrals were made in 2000 but the organisation, which replaced the Serious Organised Crime Agency, expects to deal with 380,000 this year.

Taking evidence from Keith Bristow, the NCA’s director general, committee chairman Keith Vaz claimed the “criminal elements must be rubbing their hands with glee … People are actually getting away with criminal activity, aren’t they, because of your agency’s failure to monitor all these cases that come before you?”

National Crime Agency reviews warrants after major trials collapse

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He added: “The public out there may feel here we are, we are supposed to have created a new FBI but the level of incompetence that has been shown in the cases is a serious worry.

“The arrival of all these officers at people’s homes with warrants that are not really valid, it’s more Keystone Cops, isn’t it, than FBI?”

Bristow, whose appointment was announced in 2011, admitted the organisation had fallen well below the standards the courts would expect in two investigations but insisted the organisation was a success and had a 92.8% conviction rate.

He added: “We decided we would, because we are a responsible agency and we want the highest standards, review all of our live investigations where there was a similar type of application for a warrant or a production warrant.”

Six of Bristow’s most senior colleagues are also leaving or have left with more than 100 junior staff.

• This article was amended on 9 December 2015 to clarify that Keith Bristow, the NCA’s director general, was actually appointed in 2011.